This invention relates to magnetic fluid.
Among magnetic fluids are known colloidal dispersions of fine particles of magnetic oxide material, typically magnetite (Fe.sub.3 O.sub.4) pretreated with a surface-active agent in oil or water. Such magnetic fluids have been utilized in a variety of applications.
As is well know in the art, magnetic fluids often find applications as sealing materials for sealing of rotary shafts or the like. In these applications of magnetic fluids, it is often required that the mediums be low volatile, thermally stable and lubricant. Fatty acid mono- and di-esters as well as polyphenyl oil are well-known mediums which meet the above requirements. In fact these mediums have been used for producing magnetic fluids with magnetic oxide materials dispersed therein.
However, no attempt has been successfully made in producing magentic fluids meeting the above requirements by dispersing magnetic particles in the form of metal fine particles which themselves have high saturation magnetization. If magnetic fluids can be produced by dispersing a high concentration of metal fine particles in the above mentioned mediums, such magentic fluids which have increased saturation magnetization and superior thermal stability would find a wider variety of applications.
Metal fine particles in these magnetic fluids are expected to be oxidized with a probable reduction in saturation magnetization.